1. Field of the Invention
The present invention relates to an ultrasonic atomizing apparatus used for a moistening device or the like which atomizes liquids such as water by ultrasonic vibrations to moisten it.
2. Description of the Prior Art
FIG. 9 is a schematic view showing a conventional construction of a home moistening device, which has a box-like body 80 interiorly provided with an atomizing tank 81. The atomizing tank 81 has an ultrasonic vibrator 82 mounted on a bottom plate thereof. The body 80 is provided on the bottom portion with a power transformer 83, an electric fan 84 for blowing air to the atomizing tank 81 and a driving circuit 85 for the vibrator 82. The body 80 is provided on the upper portion with a water tank 87 storing water 86 therein. A discharge pipe 88 is provided adjacent the water tank 87. The water tank 87 is provided on the bottom plate with an automatic water valve 89. The body 80 is provided on the lower portion with an air intake opening 91, through which air taken in from the fan 84 passes a portion of the driving circuit 85 as indicated by the arrow to cool a vibrator driving power transistor. The air is then introduced into the atomizing chamber 81 so as to carry a mist through the discharge pipe 88 from a water column 90 generated by action of the vibrator. A preferable depth of water 86 within the atomizing chamber 81 is decided according to the vibratory frequency of the vibrator 82 and the vibrator power of a radiation area (generally, in the range of 1.8 MHz to 2.4 MHz). The ultrasonic vibrator 82 and the driving circuit 85 constitute an ultrasonic atomizing unit 110.
Recently, the conventional ultrasonic atomizing apparatus which is used as a home moistening device, is very popular due to its fine mists generated therefrom. However, most of these apparatuses are manufactured with an assuption that the apparatus is set in a room of 3.3 m.times.4 m or 13.2 m.sup.2. The apparatus has a discharge of approximately 400 cc/H to meet the room size. The apparatus is designed so that when it is operated at the maximum rate with the water tank 87 fully filled with water, the apparatus will continue to operate for eight hours. Therefore, the capacity of the water tank 87 required is from 4 l to 5 l. Further, since the water tank 87 is installed on the atomizing chamber 81, a large cavity 92 is formed between the power transformer 83, the fan 84 and the water tank 87, thus forming the apparatus into a relatively large size as a whole. If a room is partitioned into small rooms of 3.3 m.times.3 m (9.9 m.sup.2)m to 2.25 m.times.3.3 m(7.425 m.sup.2) or a heater is provided in the room, one moistening device is necessary for each room. However, in prior art apparatus, the space occupied by the apparatus is large, the moistening capacity of the apparatus is excessively large for a narrow room, and a cost thereof is high. This makes it impossible to use a moistening device for each room, which poses a problem because one unit of a moistening device is forced to be placed in a relatively large room such as a living room.
Next, the construction and problems of the ultrasonic atomizing unit 110 used for the aforesaid apparatus will be discussed in connection with FIGS. 10 and 11.
FIG. 10 shows one example of an ultrasonic moistening device which uses a conventional ultrasonic atomizing unit, and FIG. 11 is a plan view of an ultrasonic atomizing unit portion thereof. In FIGS. 10 and 11, reference numeral 101 designates a metal base having a large wall-thickness such as aluminum die casting. An ultrasonic piezo-electric vibrator 103 in the form of a disc-like piezo-electric ceramic is mounted on the metal base 101 through a resilient support 102. Here, the vibrating surface of the piezo-electric vibrator 103 is arranged to be inclined with respect to the metal base 101 (i.e., inclined with respect to the surface of water to be atomized). A print substrate 104 is connected by means of screws to one end of the metal base 101, and a driving circuit 105 is assembled on the print substrate. The thus constructed ultrasonic atomizing unit 110 is water-tightly secured to a mounting hole 113 in the bottom of a water tank 112 storing water 111.
It is noted that the vibrating surface of the piezo-electric vibrator 103 is inclined with respect to the water surface in order to enhance the atomizing efficiency. That is, atomization is effected in the vicinity of the forward end of a water column 114 caused by ultrasonic waves but if the vibrating surface of the vibrator 103 is not inclined, the water column 114 rises vertically, in which case large water droplets, which are not atomized, fall on the water column to deteriorate the atomizing efficiency. To prevent this, the vibrating surface is inclined to incline the water column to prevent the unatomized large water droplets from directly falling on the water column, thus enhancing the atomizing efficiency.
In the aforementioned atomizing unit, the driving circuit is arranged below or laterally of the piezo-electric vibrator. In either case, both the elements are connected by a lead wire. This increases an occupying area of the unit. As a consequence, a problem arises in that the incorporated apparatus becomes large.
Furthermore, when the vibrating surface of the vibrator 103 is inclined, the inclining direction of the water column 114 is defined according to the type of an ultrasonic moistening device, for example, according to the construction of an atomizing chamber or the like. However, in the conventional construction as shown in FIGS. 10 and 11, since the print substrate 104 or the like is mounted geometrically asymmetrically with respect to the center of the vibrator 103, it is difficult to mount the ultrasonic atomizing unit 110 rotated on the body portion of the ultrasonic moistening device in order to take precedence of the inclining direction of the vibrating surface of the vibrator 103. Therefore, in the past, four kinds of ultrasonic atomizing units are assembled having a piezo-electric vibrator inclining in at least four directions, as indicated by arrows A, B, C and D. Therefore, in assembling, four ways of assembling have to be carried out always in consideration of the inclinding direction of the piezo-electric vibrator, which poses further problems in that the assembling work is cumbersome and the volume production is impaired.
The present invention has been achieved in view of the foregoing, and it is an object of the invention to provide an ultasonic atomizing apparatus which can be miniaturized and which can be produced in volume.